The invention relates to a method of controlling an electromechanical actuator. It relates further to a method of shaping an alternating voltage, an actuator for maneuvering a mobile appliance of a building in a first direction and in a second direction, comprising a motor drive unit and a motor and installations for implementing the methods.
Single-phase asynchronous motors are commonly integrated within the actuators used for comfort and/or security applications in a building, such as for example the operating of shutters, roller blinds, ventilation flaps or closures.
Patent application WO2004/025867 describes more particularly a method relating to actuators capable of operating a mobile element in two directions of rotation and comprising two power supply terminals. A control to move in a first direction (for example up) is transmitted by cutting off the negative half-waves while a control to move in a second direction is transmitted by cutting off the negative half-waves. A stop control is obtained by cutting off the supply voltage completely for a duration lying in a determined time interval.
This method and the means presented for its implementation comprise several drawbacks. Implementation requires special switches for generating a stop control. The special switch comprises a third contact, for example normally closed, or comprises a mechanical means allowing simultaneous pressing of the two movement control contacts. Moreover, during the transmission of a movement control command, if the user maintains his action on the contact, the motor is firstly powered under reduced effective voltage and consequently might not deliver sufficient torque to allow the motor to start. Thereafter, the permanent powering of the actuator takes no account of the energy economy requirements. Furthermore, the installation using the method is not secure against an outside intrusion attempt or against the glitches that may arise on the power supply line. Finally, insofar as it is necessary that the electronics downstream of the switch be always powered, a movement stop command consisting of opening the line can only be transmitted for a very reduced duration. In the event of fleeting failure of the reception means, it is possible that this stop command may not be received. This is a serious security problem.
Another major drawback of the prior art is that it requires that the diodes contained in the special switches be dimensioned as a function of the rating of the current absorbed by the motor. In particular, it is almost impossible for several motors supplied by one and the same switch to be placed in parallel unless said diodes are overdimensioned. In the case of a general control switch, placed upstream of the installation, the nominal rating of the diodes becomes considerable: specifically, a motor used in the applications cited absorbs a typical current of 1 A, this corresponding to a very cheap standard diode 1N4007, while an installation of 20 motors will require bulky and expensive 20 A diodes.